The present invention relates to a light deflector for causing incident light to be deflected in a desired direction by tilting a reflective mirror in the direction of x-or y-axis in a plane in response to an applied electrical signal. More particularly, the present invention relates to such a light deflector that can be used in projecting an image in the space by causing an abrupt change in the direction in which a laser light travels.
A light deflector for tilting a reflective mirror by means of bimorph cells is disclosed in Japanese Patent Publication No. 40215/1977. FIG. 1 is a diagrammatic cross section of this conventional light deflector; a pair of bimorph piezoelectric cells a which will bend upon voltage application are fixed at one end and connected at the other end to the periphery of the bottom of a reflective mirror b for supporting the same; the mirror b is caused to tilt by the bending action of each bimorph cell a.
In the arrangement described above, the reflective mirror b and the piezoelectric cells a are supported only by means of fixing the cells at one end. This arrangement is weak and the piezoelectric cells a may easily break if an external force is concentrated in the center. If the thickness of the reflective mirror b is reduced to ensure the application of a minimum load on the cells a, the physical strength of the mirror b is also reduced to present considerable difficulty in handling. The amount of tilting of the mirror b is determined by many factors such as the voltage applied to the cells a, the distance between the fixed end of each cell and the periphery of the mirror b on which it is supported by the cells, and the weight of the mirror b, and because of this complexity in determinants, it is substantially difficult to achieve the desired precision in tilting position. A further disadvantage results from the fact that the center load of the mirror b will prevent it from being tilted to a great extent.